The present invention relates to a sealing element and a holding-down clamp.
German Published Patent Application No. 197 35 665 describes a sealing element. The sealing element is formed by a peripheral radial groove provided on a nozzle body of a fuel injector inserted into a receiving bore and a sealing ring inserted into the groove. The sealing ring is prestressed in the radial direction and is supported in the groove of the nozzle body as well as on the wall of the receiving bore.
One disadvantage of the sealing element described in German Published Patent Application No. 197 35 665 is that the prestress on the sealing element depends on the geometry and in particular on the diameter of the receiving bore. Therefore, the conventional sealing element cannot be used universally but instead must be adapted specifically for each receiving bore. In addition, the prestress on the sealing element cannot be adjusted, so the prestress varies due to aging or due to manufacturing tolerances and thus the seal may not be adequate. In addition, the seal is exposed directly to the hot exhaust gases, which results in accelerated aging of the sealing ring. In addition, with the conventional sealing element, penetration of the sealing element may occur in particular because of the almost circular cross section of the sealing element.
Another disadvantage is that due to the radial prestress on the sealing element, there is a frictional force which counteracts an axial displacement of the sealing element. This greatly interferes with both installation and removal as well as adjustment of the fuel injector. Because of soiling deposits on the sealing element and aging of the sealing element, it may even be no longer possible to remove the fuel injector, or the sealing element may be destroyed during removal of the fuel injector.
German Published Patent Application No. 197 43 103 describes a sealing element designed as a thermal insulation sleeve. The thermal insulation sleeve is inserted into a stepped receiving bore of a cylinder head of an internal combustion engine and surrounds peripherally a nozzle body on the spray end of a fuel injector inserted into the receiving bore. The tubular thermal insulation sleeve is bent on the spray end to form a double layer of the sleeve. The double layer of the sleeve is under prestress radially against the wall of the receiving bore to seal the annular gap formed between the nozzle body and the receiving bore. To produce this prestress, the nozzle body of the fuel injector has a conical section which is inserted into the sleeve and is jammed in the sleeve in the area of the bent portion of the sleeve. The fuel injector is also in contact with an inclined step to secure the position of the fuel injector in the receiving bore.
One disadvantage of the fuel injector described in German Published Patent Application No. 197 43 103 is that the thermal insulation sleeve is prestressed in the area of the double layer of the sleeve between the nozzle body and the receiving bore. This results in the problems mentioned above when installing or removing the fuel injector. Another disadvantage is that the position of the fuel injector and the receiving bore is fixedly predetermined. Because of manufacturing tolerances, the axis of the fuel injector introduced into the receiving bore does not in general exactly match the axis of a connection piece of a high-pressure fuel line. Therefore, an additional adaptor is necessary for connecting the fuel injector to the high-pressure fuel line. Japanese Published Patent Application No. 8-312503 describes a holding-down clamp. This holding-down clamp holds a fuel injector down against a relatively high combustion pressure prevailing in the combustion chamber of the internal combustion engine. The holding-down clamp acts on a collar of the fuel injector at two diametrically opposed locations, the lower side of the collar being in contact with the upper side of the cylinder head, so that the fuel injector is secured.
The holding-down clamp described in Japanese Published Patent Application No. 8-312503 has the disadvantage that it acts on the fuel injector only in the axial direction. In the case of a mechanical load on the fuel injector, the fuel injector may therefore be twisted, tilted or displaced in the radial direction. The fuel injector may therefore become loosened at the point of connection and the high-pressure fuel line may be displaced. In addition, there may be an unwanted load on the sealing element. In the case of a sealing element designed as a sealing ring which is in contact with both the fuel injector and the wall of the receiving bore, shearing stresses build up peripherally during rotation of the fuel injector in the sealing ring, thus worsening the sealing properties of the sealing ring.
German Published Patent Application No. 197 35 665 also describes a holding-down device designed as a tension claw like the holding-down clamp described in Japanese Published Patent Application No. 8-312503. In the case of German Published Patent Application No. 197 35 665, the cylinder head has a recess in which the collar of the fuel injector is situated, so the collar of the fuel injector on which the holding-down device acts is lowered into the cylinder head. The disadvantages described above also apply to this holding-down clamp.
A sealing element according to the present invention may provide the advantage that the fuel injector may be installed into and removed from the cylinder head with no problem, because the sealing element is not under any prestress in the radial direction against the wall of the receiving bore of the cylinder head, so that the sealing element does not interfere with installation and removal. In particular, special tools are thus no longer necessary for installing and removing the fuel injector.
Another advantage may be that the prestress on the sealing element may be predetermined, thus lowering the demands regarding production accuracy. In addition, a fuel injector having the sealing element according to the present invention may be used universally.
The sealing properties of the sealing element may be independent of the location of the fuel injector and the receiving bore so that it is possible to compensate for an axial offset, for example, with no problem.
A holding-down clamp according to the present invention may provide the advantage that the position of the fuel injector and in particular the rotational position of the fuel injector are secured. In addition, the holding-down clamp also acts on the fuel injector in a manner that is at least approximately uniformly distributed around the circumference, so that tilting of the fuel injector is prevented.
The axial height of the recess may be at least essentially equal to half the axial height of the base body of the sealing element. This results in a good sealing effect and a good stability of the sealing element. In addition, it is possible for a radial prestress on the sealing element to act on the nozzle body over a large area.
The radial width of the recess may be at least essentially equal to half the radial width of the cross section of the base body in the area of the recess. This makes it possible to achieve a high elasticity of the sealing element, which is provided by the sealing element, together with a high stability of the sealing element, which is provided essentially by the base body.
The base body may be configured as a metal block. Therefore, the sealing element is configured to be heat resistant and to have dimensional stability. In addition, the sealing element also has a great mechanical load bearing capacity.
As an alternative, the base body may be configured as a spring plate. Therefore, the sealing element may be manufactured easily and cost effectively. In addition, with a suitable configuration of the sealing element, the base body configured as a spring plate may be under prestress.
The base body may have a sleeve at the ends of which a collar is formed. This may provide a support of the base body over the collars on the fuel injector and on a step of the receiving bore.
The sealing element may be partially in contact with the second contact surface of the base body. The sealing element of the seal may therefore assume the function of axial sealing as well as the function of radial sealing.
The sealing element may be made of a heat-resistant plastic, e.g., a fluoroelastomer or a fluoroelastomer based on a vinylidine fluoride-hexafluoro-propylene copolymer. The sealing element may be bonded to the base body by vulcanization. The sealing element may be manufactured as follows, for example. First, the starting plastic material, e.g., in the form of a powder or granules, is applied to the base body, and then the starting plastic material is vulcanized, forming a heat-resistant plastic which adheres to the base body. The surface of the base body may be prepared accordingly, e.g., by roughening.
The sealing element may be made of polytetrafluoroethylene (PTFE). This creates a heat-resistant sealing element which is simple to manufacture and is resistant to combustion gases because of its extremely high resistance to chemicals.
The sealing element may be under prestress in the axial direction by way of the base body in the installed state of the fuel injector. Therefore, it is possible to further improve on sealing with this sealing element, in particular in the radial direction.
The base body may be in contact with the step of the receiving bore by way of a sealing sheet. The sealing sheet may be made of a soft metal, e.g., copper. This permits a further improvement in the seal. In addition, the sealing element is protected by the sealing sheet from direct contact with the hot combustion gases and the temperature of the combustion gases.
The housing part may be arranged on the side of the fuel injector facing away from the fastening element. Therefore, the fastening partial ring may surround the fuel injector on two sides, providing a good transfer force from the fastening element to the fuel injector.
The fastening partial ring may have a peripheral inner shoulder which works together with a peripheral shoulder on the fuel injector to prevent tilting of the fuel injector. Therefore, the force of the holding-down clamp is transmitted at least almost uniformly to the fuel injector around the perimeter.
The fastening partial ring may have an inside surface with which the fuel injector is at least essentially in surface contact to prevent displacement of the fuel injector in a radial direction. Due to the surface contact of the fuel injector with the inside surface of the fastening partial ring, tilting of the fuel injector is also prevented.
The base body may be configured so that the sealing element is close to the tip of the valve. This permits a reduction in the dead volume or the HC pockets.
The base body may function as a heat sink to dissipate the heat from the fuel injector, e.g., in the area of the nozzle body.
The base body may be mounted in contact with the cylinder head to further improve cooling of the valve body.
The holding-down clamp may be arranged at least partially in the receiving bore, and the inside surface of the holding-down clamp is essentially in contact with the fuel injector in an area within the receiving bore. The holding-down clamp may therefore be countersunk at least partially into the receiving bore of the cylinder head, so that the fuel injector may have a more compact configuration. In addition, this facilitates assembly and permits better protection of the holding-down clamp.